Background to the Invention Underwater engineering operations often require that a torque be applied to elements or items of the equipment being worked on, for example bolts/nuts on pipe flanges, operating spindles for valves etc.

Such operations are conventionally carried out by Remotely Operated Vehicles (ROV's) using a torque tool. This is carried in a suitable Tool Deployment Unit (TDU) that is mounted on the ROV, or alternatively, the torque tool is gripped by the end effector of a manipulator arm of the ROV, where the

ROV transports the tool to the work site. Once there, the torque tool is manoeuvred by the TDU or manipulator arm so that its end effector is positioned over or connected to the item (such as a nut, spindle etc. ) that is to be rotated. The torque is then applied by control of a rotary drive mechanism contained within the torque tool, and supplied with power from the ROV.

The conventional torque tools are hydraulically driven, and consequently are deficient in torque at low speeds, this typically being a characteristic of hydraulic motors of a design suitable for these applications. They are not therefore ideally suited to providing the high torque needed to overcome such resistance as might arise from a damaged thread, tight seals on a valve spindle etc. This is particularly so when starting or finishing a rotating operation since the drive is essentially static.

It is an object of the present invention to overcome the disadvantages of conventional torque tools.

Summary of the Invention According to a first aspect of the present invention there is provided a torque tool for driving an item to be rotated, the torque tool comprising:- an electrical transverse flux motor; and

a coupling mechanism for coupling with the item to be driven, such that actuation of the electrical transverse flux motor results in rotation of the coupling mechanism.

Preferably, the torque tool further comprises a gearbox either integral with or coupled to the electrical transverse flux motor such that actuation of the electrical transverse flux motor results in rotation of the coupling mechanism via the gearbox.

Typically, the item to be driven is underwater and preferably, the electrical transverse flux motor is encased in a housing which is preferably a sealed housing.

According to a second aspect of the present invention there is provided a torque tool for driving an underwater item to be rotated, the torque tool comprising:- an electrical motor; a gearbox either integral with or connected to the electrical motor; at least the electrical motor being encased in a sealed housing; and a coupling mechanism for coupling with the item to be driven, such that actuation of the electrical motor results in rotation of the coupling mechanism via the gearbox.

Preferably, the electrical motor is an electrical transverse flux motor and the gearbox is preferably an epicyclic gearbox although the gearbox may alternatively be a cycloidal gearbox or any other suitable gearbox.

Typically, the gearbox is also encased in a sealed housing, which is preferably the same sealed housing as that encasing the electrical transverse flux motor. Typically, a shaft output of the gearbox protrudes from the sealed housing and is connected to the coupling mechanism outside of the housing.

Typically, the electric motor comprises a rotational output shaft that is connected to, or itself comprises, a rotational input shaft of the gearbox.

Preferably, the gearbox comprises a rotational output shaft that is connected to, or itself comprises, a rotational input shaft of the coupling mechanism. More preferably, the longitudinal axis of the rotational output shafts of the electric motor and the gearbox are coincident with one another. Typically, the longitudinal axis of the rotational input shafts of the gearbox and the coupling mechanism are coincident with one another.

Preferably, the longitudinal axis of the rotational output shafts and the longitudinal axis of the rotational input shafts are also coincident with one another.

Typically, the housing is provided with a cooling means which may in preferred embodiments comprise one or more cooling fins or the like.

Preferably, the sealed housing is filled with a fluid, which is preferably a lubricating fluid such as oil. Typically, the housing is provided with a lubrication fluid pressure compensation system which maintains the pressure of the lubrication fluid within the housing at, close to, or just above the ambient pressure outside of the housing. Typically, the housing comprises a seal system to prevent ingress of water into the housing from the outside environment and/or to prevent loss of oil to the outside environment.

Typically, one or more of the input and/or output shafts are provided with one or more transducer device (s) and/or one or more resolver device (s) which measure the torque experienced by the said shaft (s) and/or measure a rotor angle. Preferably, a control system is further provided which controls the supply of electrical power to the motor and/or the direction of rotation of the motor and/or the number of turns the coupling mechanism is to perform. Typically, the control system is connected to the said transducer and/or said resolver device (s) and provides power and signals to the motor partly, mainly or wholly based upon the signals provided by the said transducer and/or said

resolver device (s) whilst comparing said provided signals with the operator input commands.

Preferably, the coupling mechanism is further provided with a selective latching and/or rotational locking mechanism in order to ensure the torque tool and the item to be driven are secured to one another whilst the item is being driven. More preferably the selective latching and/or rotational locking mechanism provides a support against which the torque generated by the torque tool can react.

Typically, the item to be driven is provided with formations to facilitate said selective latching and/or rotational locking.

Preferably, the transducer device is connected at one end to the gearbox and at the other end to a portion of the coupling mechanism that reacts the applied torque, and more preferably, the said portion of the coupling mechanism is the selective latching and/or rotational locking mechanism. This has the advantage for embodiments of the invention that the transducer device is subjected to the full reaction torque.

Optionally, the coupling mechanism is adapted to accommodate the item to be driven which may be a nut or spindle etc. Alternatively, the coupling mechanism may connect to components of subsea equipment such as a wellhead in order to actuate said components.

Embodiments of the invention have the advantage that the electrical transverse flux motor has a much better torque characteristic at low speeds than other motors. Thus, embodiments of the invention have the advantage that they provide a wider range of torque than previously possible for the same size/weight of other units. Furthermore, embodiments of the invention have the advantage that the torque and/or the rotation angle/turns can be very accurately applied. Additionally, embodiments of the invention have the advantage that an electric tool will be more compatible with the all-electric workclass ROV's that are planned to replace the earlier hydraulic based models.

Brief description of the Drawings Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a cross-sectional side view of a first embodiment of a torque tool in accordance with the present invention and a schematic diagram of a control system for controlling the torque tool; Figure 2 is a three dimensional flux path for a Transverse Flux Motor of the torque tool of Figure 1 ;

Figure 3 is a perspective cut-away view of an example of a three phase Transverse Flux Motor of the torque tool of Figure'1 ; Figure 4 is a perspective exploded view of an example of an epicyclic or planetary gearbox of the torque tool of Figure 1; Figure 5 is a cross-sectional view of an alternative embodiment of a torque tool in accordance with the present invention; Figure 6 is a further and more detailed cross- sectional view of a latching mechanism of the torque tool of Figure 5 during actuation thereof; and Figure 7 is a cross-sectional view of the latching mechanism of Figure 6 after actuation; and Figure 8 is a further detailed cross-sectional view of the latching mechanism of the torque tool of Fig. 5 during actuation thereof.

Detailed Description of the Drawings Figure 1 shows a first embodiment of an electric torque tool 1 in accordance with the present invention as comprising a transverse flux motor 2 at it's core. The transverse flux motor 2 has a resolver 5 built into the drive end of the motor 2.

The purpose of the resolver 5 will be detailed subsequently.

Unlike a conventional LFM (longitudinal flux motor) the TFM (transverse flux motor) 2 has a magnetic flux path with sections where the flux is transverse to the rotation plane. Figure 2 shows a representative three dimensional flux path for the TFM motor 2, in which the flux flow path flows through the rotor 60, and the stator 62. The flux flow path is generated by a combination of the magnetic flux created by an electrical current flowing through the stator windings 64 and the magnetic flux provided by the permanent magnets 66 provided on the rotor 60. In contrast, in an LFM motor such as an induction or DC machine, the lines of flux follow a two dimensional pattern in planes perpendicular to the motor shaft. The TFM motor 2 is also known as VRPM (variable reluctance permanent magnet) motor 2, and a part cut-away perspective view of the internal components of the TFM 2 is shown in Figure 3.

In the TFM motor 2, as shown in Figure 2, the lines of flux follow a more complicated dimensional pattern which results in the decoupling of the space occupied by the armature winding. The unusual characteristic of this TFM motor 2 is that the rotor 60 is on the outside and the stator 62 is in the centre. The TFM motor 2 with the same power rating is one third to one fifth in size and weight compared to conventional LFM motors.

Although the flux path in a TFM motor 2 is more complicated than in a LFM motor the flux path in a

TFM motor 2 is much shorter. This allows higher flux densities to be achieved in the air gap which in turn results in a greater torque being produced.

The high torque and low speed characteristics of the TFM motor 2 enables the use of a single gearbox and a reduction ratio of around 100: 1. The other principle benefit of the lower speed is a reduced inertia effect and less risk of damage to the gearbox when end stops are reached. The TFM motor 2 is preferably an active rotor type TFM 2 with permanent magnets 66 on the rotor 60.

This TFM motor 2 uses a resolver 5 (as seen in Figure 1) as the signal generator for a commutation controller. Because the resolver 5 does not rely on optical signal processing, it can operate successfully in an oil filled environment. Such oil filling provides a pressure balancing capability which means the motor 2 can be used at deep depths without the need for pressure resistant housings, and complex high pressure shaft seals, as will be detailed subsequently. The oil filling also improves the motor 2 cooling, and advantage can be taken of this to use the motor 2 in an overload mode for short term application (e. g. to overcome the -initial stiction of a valve operating shaft). As seen in Fig. 8, seals 68 are provided on either side of the latching sleeve 166 between the latching sleeve 166 and the torque tool housing 12 in order to prevent oil from passing therebetween due to any residual pressure difference across the torque tool

housing 12 which has not been compensated for by the compensator 20.

The electronic commutation also facilitates software control of the motor 2. Consequently, the parameters of tool 1 operation-such as torque to be applied, the direction of application, and the angular rotation to be achieved-are readily pre- set, and the tool 1 output delivered accordingly.

A motor output shaft 3 projects outwardly from the motor 2 and is connected to the input shaft of an epicyclic gearbox 4 which is mounted in a gearbox case 10. However, it should be noted that, although the epicyclic gearbox 4 is preferred in this embodiment, a cycloidal gearbox or any other suitable gearbox could be used instead.

The epicyclic gearbox 4 (sometimes also known as a sun and planet gear) is especially suitable for high torque applications due to all of the radial forces occurring in the gearbox 4 being balanced.

Different drive ratios can be achieved with the same gearbox 4 by fixing the appropriate elements of the different parts of the gear mechanism, as discussed below.

Figure 4 shows the main features of a typical epicyclic gearbox 4. At the centre is a'Sun'gear which meshes with the three'Planet'gears that run on spindles on the planet carrier. These gears in

turn mesh with teeth of the outer'Ring'. If all of the gear carriers are locked together, the input and output shafts of the box rotate at the same rate.

The overall gear ratio would then be expressed as 1: 1. Fixing the planet gear carrier and allowing independent rotation of the sun and ring gears gives them a relative rotation rate determined by their tooth counts, Ns and NR. This overall gear ratio is (NR/Ns).

Fixing the sun gear, and using the planet carrier and ring as input and output shafts gives another overall gear ratio: (Ns/NR) + 1.

A final ratio may be obtained by fixing the ring and allowing the sun gear and the planet carrier to rotate.

For this configuration the overall gear ratio is: (NR/Ns) + 1.

The number of teeth on the gears is constrained by the meshing requirement so that: NR = (NS + 2NP).

Also: (NR + Ns)/# of Planets = must be an Integer.

The epicyclic gearbox 4 provides high torque at very low speed, which is highly desirable in this embodiment.

A gearbox output shaft 7, which provides the rotational output of the epicyclic gearbox 4, is coupled to the innermost end of an end effector 6

which, in use, is coupled to the item to be driven/rotated 31.

The gearbox 4, in essence, is used to magnify the torque output from the motor 2, as generated at an end effector 6. The end effector 6, which is attached to the gearbox output shaft 7, runs in a bearing 8, mounted in a tool nose piece 9. The gearbox case 10 is connected to one end of an annular torque transducer 11, the other end being connected to the nose piece 9. This configuration ensures that the torque transducer 11 is subjected to the full reaction torque. The purpose of the annular torque transducer 11 is to provide an indication via a signal line of the torque being generated at the gearbox output shaft 7, as will be detailed subsequently.

As can be seen in Figure 1, the nose piece 9 comprises an open outermost end (the right hand end as presented in Figure 1) such that there is an annular gap or space between the outermost surface of the end effector 6 and the inner bore of the nose piece 9. This annular space is provided in order to accept an annular receptacle 32 provided about the item to be driven 32, such that the receptacle 32 safely guides the nose piece 9 and thus the end effector 6 into engagement with the item 31. A longitudinally extending key 33 is provided on the upper most side of the receptacle, the key 33 being for engagement into a longitudinally extending slot

formed along the inner bore of the nose piece, wherein the key 33 and slot co-operate to ensure the item 31 and the end effector 6 are rotationally aligned prior to and during engagement occurring therebetween. In addition, the co-operation between the key 33 and the slot provides the distinct advantage that the applied torque can be fully reacted by the tool 1/receptacle 32 combination.

The transverse flux motor 2, gearbox case 10 and thus the gearbox 4, and the annular torque transducer 11 are encased in a cylindrical cover 12 which is fitted with cooling fins 15 to prevent overheating of the said components 2,10, 4,11 within. A pierced cylindrical frame 14 surrounds the outside rear portion of the cylindrical cover 12 in the form of a sleeve, and the pierced cylindrical frame 14 is further mounted at it's upper end to a TDU connection 16. Resilient mounts 13 are provided between the outer cover 14 and the cylindrical cover 12. These give a level of flexibility that facilitates deployment of the end effector 6 on to an item to be driven 31 (shown in phantom in Figure 1). A TDU (not shown) is connected to the TDU connection 16 and the TDU provides precision movement of the tool in x, y, and z directions, and thus ensures the accurate alignment required for trouble free engagement of the end effector 6 with the item to be driven 31. However, it should be noted that the electric torque tool 1 will more usually be gripped by the jaws (not shown) of an end

effector of a manipulator arm (not shown) provided on the ROV.

Chambers or spaces 17 and 18 within the cylindrical cover 12 and the transducer 11 are interconnected and oil filled, the oil being retained at the output shaft 7 by a lip seal 19. A compensator 20 is connected to the chamber 17 by a tube 21, its function being to ensure that the torque tool 1 is always full of oil at just above ambient sea pressure, and thus is pressure balanced.

Consequently the tool 1, unlike an atmospheric unit, can be used at deep depths without the need for the containment provided by the cylindrical cover 12 etc. , or the shaft seal 19, to be capable of resisting high pressure. This has the advantage that the tool weight can be kept to an acceptable low level-i. e. it can be readily accommodated by an ROV (not shown). It also ensures that friction losses through the shaft seal 19 are very low, thus ensuring that the delivery of torque to the end effector 6 is as close as possible to that indicated by the torque transducer 11.

The compensator 20 comprises a piston (A) sealed by a rolling diaphragm (B) within a cylindrical container (C), which is closed at both ends. Also contained within the cylinder (C) is a compression spring (D) that bears on one side of the piston (A).

The spring end of the cylinder (B) has a central opening (E) that provides a connection to the

surrounding sea. The other end is fully closed and connected by the pipe 21 to the tool 1. Because of the sea acting on the spring side of the piston (A) the space or chamber (F), which is oil filled, is- also at sea pressure. As this space or chamber (F) is connected to the tool 1 by the pipe 21 it follows that the oil in the spaces or chambers 17,18 is also at sea pressure. The tool body/cylindrical cover 12 is therefore pressure balanced and remains so as the ROV changes depth-up or down. This avoids the need to construct a pressure proof containment for the tool 1 components, and consequently the overall weight is kept to an acceptable minimum. It also avoids the complexity of providing a high pressure seal 19 on the output shaft 7. In practice, because of piston friction (A), the actual oil pressure is slightly lower than the sea pressure. The spring (D) has been incorporated to apply an additional load to the piston (A), so that the oil pressure is kept at a level just above sea pressure at all times. This ensures that any fluid leakage from the system is of oil outwards into the sea, and not of sea water inwards into the oil (and the tool 1).

The resolver 5 is used to measure the rotor angle for an electronic motor control system 22, which is located on the ROV, and which replaces the more conventional carbon brushes as a means of providing motor commutation. The resolver 5 continuously monitors the rotor angular position at any given time. The control system (described subsequently)

translates this information into the position of the rotor magnets relative to the stator poles. The latter are then switched sequentially north/south to ensure the rotor rotates at the required speed and in the required direction. The resolver 5 therefore provides accurate information on the motor 2 rotation, thus enabling accurate control of the end effector 6.

The motor 2, resolver 5, torque transducer 11, and the various controls are interconnected by the cables 23,24, 25, 26, and 27. Cable 27 is in the form of an umbilical from the ROV to a surface control suite (not shown) mounted on an ROV support ship/vessel (not shown) at the sea surface. The cables 23, 24,25 are connected to the tool 1 by a waterproof connector 28 which extends through the cylindrical cover 12 from the outside and through a rear sidewall of the pierced cylindrical frame 14, into the chamber 17. Power is supplied to the tool 1 from the ROV via cable 29, and the control box 22 mounted on the ROV, the control box 22 providing the necessary commutation and direction of rotation signals etc to the tool 1.

The core elements of the tool control system are the commutation system 22 located in the control box 22 and the surface control suite/console 30 located on the ROV support vessel. The control system 22,30 is arranged to:

a. Provide a means of setting and accurately generating the required torque profile; b. To provide an automatic shut off when a pre-set torque figure is achieved; c. Setting of the required direction of rotation, and number of turns; d. Protect the system from damage; e. Provide interlocks as required; f. Provide manual by-pass operations as required; g. To indicate during the operation: (1). The actual and set direction of rotation; (2). The set torque; (3). The torque being applied; (4). The number of turns of the end effector; (5). The occurrence of automatic shut off, the key readouts at this point, and the cause of the shut-off (max. torque, over heating, over use etc. ) ; (6). A graphical display of the applied torque versus number of turns; (7). Warnings of: (a). Excessive use of over load; (b). Loss of pressure compensation; and (c). Water ingress.

The operation of the torque tool 1 on an ROV will now be described. The torque tool 1 is initially held in the TDU, which is flexibly connected to the outer cover 14 of the tool 1 via the TDU connection 16 or is alternatively held in the jaws of the manipulator arm, as appropriate. The ROV transports the tool 1 to the work site and once there, the ROV pilot positions the ROV so that it can be docked onto the equipment being worked on. The pilot then uses the TDU or manipulator arm to manoeuvre the end effector 6 over the item 31 to be driven (e. g. drive shaft end, bolt/nut etc. ). This action also engages the nose piece 9 with the receptacle 32, these being locked together by the key 33 so that the applied torque can be fully reacted by the tool 1/receptacle 32 combination. With the tool 1 in place, the pilot sets the required torque setting and tool rotational direction on the control console 30 and initiates the turning operation. Electrical power is then supplied from the ROV to the tool 1 via the cable 29, with the polarity/commutation being arranged by the control box 22 to drive the motor 2 in the required direction, at the requested speed, and for the requested number of turns. The motor 2 output is then controlled as needed to achieve the required result with regard to the number of turns and/or applied torque; the latter is measured by the torque transducer 11 as the static reaction torque between the nose piece 9 and the gearbox casing 10. Under normal circumstances, the control console 30 then switches the torque tool off at a pre-set torque

and/or number of turns. This operation can also be carried out in manual mode.

Embodiments of the invention have a number of advantages over existing torque tool systems. For example, maximum torque can be obtained when it is needed most-i. e. when the driven component is static or nearly so.

Furthermore, an electric toque tool 1 is more compatible with the all-electric ROV's that are replacing the earlier hydraulic based models.

In addition, an electric drive offers a wider. range of torque from the same unit, than is possible with 'the hydraulically driven equivalent. This provides a three-fold reduction in the inventory of tools that have to be held against potential contracts.

Moreover, the applied torque can be readily, accurately, and finely adjusted by controlling the motor 2 current. In particular this can be done via suitable software in the surface control console 30.

In contrast, conventional hydraulic versions require recovery of the ROV to adjust the hydraulic pressure controller, an altogether less convenient, coarser, and less accurate means of control.

Furthermore, the accuracy with which the applied torque is measured, is improved by re-configuring the tool assembly, so that all the reaction torque

is applied to the transducer 11 instead of some of it being"lost", as occurs in conventional hydraulic torque tools.

Moreover, because it is of a pressure balanced construction, the weight of the tool 1 is kept to a minimum, and friction losses (gearbox output 4 to end effector 6) are minimised.

Figure 5 shows a second embodiment of a torque tool 50 in accordance with the present invention. The torque tool 50 of Figure 5 is similar in most respects to the torque tool 1 of Figure 1 with the main differences being the latching mechanism to the receptacle of the item to be driven and only these are described below.

The torque tool 50 comprises a latching mechanism 51 which includes a pair of latches 53 arranged opposite one another about the outer circumference of the nose piece 49 of the torque tool 50. The latches 53 are pivotally mounted to the nose piece 49 by means of a plurality of respective pivots 55 such that, ordinarily, the latches 53 would be free to partially rotate about an axis perpendicular to the radius of the nose piece 49 at the location of the respective pivots 55. The outer most end of the latches 53 (i. e. the end distal from the pivot 55) is provided with a grab thumb 57 which points toward a cam finger 59. The pivot end of each latch 53 is provided with a two lobed cam 61 and a driving disc

63 is arranged to lie in between the two lobes of the cam 61. The inner most face of the driving disc 63 is coupled to a sleeve 65 which is mounted in a longitudinally moveable manner to the nose piece 49 and the sleeve 65 has an outwardly projecting shoulder 166 at its inner most end. An annular ring electro-magnet 67 is secured to the nose piece 49 and is located about the sleeve 65 such that the sleeve 65 is moveable through the centre of the electro-magnet 67. An annular ring armature 69 is fixed to the sleeve 65, at the shoulder 166.

Operation of the magnet 67 is such that the armature 69 is moved towards the magnet 67, along the longitudinal axis away from the torque tool 50.

An item (not shown) to be driven by the torque tool 1 is housed within a receptacle 71 where the receptacle comprises a cylindrical member 73 which encircles the item and acts as protection therefor.

The cylindrical member 73 has a pair of apertures 75 formed in its sidewall opposite one another.

Thus, as the torque tool 50 moves into the inner bore of the cylindrical member 73, the finger cam 59 engages its upper surface on the lower most surface of the cylindrical member 73, and this engagement causes the latch 53 to rotate outwardly about its pivot 55. This rotation causes the thumb cam 57 to move into or penetrate the aperture 75 cut in the sidewall and pass under the rim of the aperture 75.

Simultaneously, the two lobed cam 61 is rotated

which causes the driving disc 63 to move longitudinally toward the item to be driven, which causes the sleeve 65 to move likewise and, by means of the shoulder 166, causes the armature 69 to move from the position shown in phantom as 69'to the position 69 shown in solid line in Figure 7. This movement continues until the armature 69 comes into contact with the pre-energised electro-magnet 67.

The latter"grips"the armature 69'and thus locks the latches 53 in the position shown in Figure 7.

The torque tool 50 can then be operated in a similar manner to the torque tool 1 in order to rotate the item to be driven.

After the item has been driven, the latching mechanism 51 is released by de-energising the electro-magnet 67 which releases its"grip"on the armature and thus the sleeve 65. This frees the latches 53 to rotate in the opposite direction as the torque tool 50 is withdrawn from the cylindrical member 73, and the underside of the rim of the aperture 75 contacts the lower most surface of the thumb cam 57 which causes continued rotation of the latches 53 to permit the thumb cam 57 to clear the aperture 75. Thus, the torque tool 50 is free to be withdrawn from the receptacle 71 which houses the item to be driven. Even if the electromagnet cannot for some reason be de-energised, the tool 50 can still be withdrawn, albeit with a larger retraction force than that required for normal operation.

It should be noted that additional improvements are also derived from embodiments of the present invention. For instance, to avoid the signal degradation of rotary electrical connections, the transducer 11 used to sense the torque is not mounted directly in the revolving output shaft, but instead is configured to measure the"static" reaction torque. In conventional arrangements, because the hydraulic motor is fixed to the tool casing by its"hard" (i. e. relatively stiff) feed and return connections, some of this reaction torque is"lost"in the deflection of these connections.

Consequently the measured output is lower than the actual by some 5%. Because the connections. to the. electric motor 2 are"soft" (i. e. flexible), the stiffness of the motor 2 to casing 12 connection problem is avoided, and the error eliminated.

Modifications and improvements may be made to the embodiments hereinbefore described without departing from the scope of the invention. For example, the means of locking the tool nose 9 to the receptacle 32 can be a key as shown or a similar device, or any suitable interlocking shape e. g. hexagonal. In addition, the end effector 6 can be configured to suit the required connection with the driven item 31. Additionally, the oil compensation 20 can be connected into the ROV's compensation system, rather than an individual arrangement. Furthermore, the torque transducer 11 can be any suitable annular

unit. Moreover, the gearbox 4 is preferably epicyclic, but could be a cycloidal gearbox or any other unit of the required performance.

Additionally, the TDU 16 can be replaced by a manipulator (robot) arm (not shown); this typically gives more flexibility in use, but may require higher operator skill.

In certain circumstances, if for some reason execution of the turning operation requires a higher than expected torque tool output, then the pilot would benefit from having a motor that can be "overloaded"in the short term to provide the extra emergency torque. To achieve this with a hydraulic motor, it would have to be oversized to provide the spare capacity for the occasional use. This could lead to it being unwieldy, and not well suited to ROV operations. Alternatively its operating pressure could be raised. This at best would make it liable to stoppage through damage to its mechanical components or, at worst, to catastrophic structural failure.

In contrast, embodiments of the electric motor 2 described herein can be used in the short term at torque outputs well above its continuous rating.

The software that controls the motor 2 can typically be modified to change the performance of the motor 2. For instance, the software could be modified to increase the electrical loads arising, and it may be possible to take advantage of the improved cooling

arising from the motor 2 running in oil, and enhance this attribute by installation of the cooling fins 15 on the motor casing cylindrical cover 12.

Furthermore, embodiments of the electric motor 2 described herein can be adequately protected from over-use of this additional capacity, by temperature sensors in the windings or similar techniques. In other words, the windings could be provided with temperature monitoring and protection arrangements that will prevent the motor 2 from being damaged, by over-zealous use of the additional capacity.

Additionally, the longitudinal axis of the rotational output shafts of the electric motors and the gearbox 4 need not be co-axial if for instance an offset shaft is utilised.

Furthermore, the electronic motor commutation system 22 may be housed within the same housing 12 as the motor 2 which reduces the cabling length required and the attendant radiated electrical interference.

Instead of driving items via an end effector 6, embodiments in accordance with the present invention may be incorporated into other equipment and the outer end of the gearbox output shaft 7 can be coupled directly to components thereof, in order to allow actuation of those components directly as and when necessary. In this configuration, such embodiments of the apparatus may be semi-permanently installed into the equipment in such a way that it

can be easily replaced if necessary. If the equipment is located in the subsea environment the replacement operation may be carried out by e. g. an ROV.